The present invention relates to a measurement transducer with a monitoring function—in particular, a measurement transducer of industrial process measurement technology with a monitoring function. Measurement transducers of industrial process measurement technology are commonly used in process control systems to measure measured variables, such as pressure, flow rate, filling level, temperature, and material parameters, such as pH, conductivity, toughness, density, humidity, proportion of dissolved gas, or mixing ratio of components, and to output a measured value representing the measured variable. In particular, with safety-critical applications, more stringent requirements are established to make sure that the operation of the measurement transducer is being monitored, to the effect that an error with the measurement transducer does not remain undetected. This includes, for example, the certification of measurement transducers according to the so-called SIL standard of the international standard IEC 61508 on functional safety. For example, monitoring concepts for measurement transducers are described in European patent EP 2 613 463 A2, published international applications WO 2005/017851 A1, WO 03/060851 A1, and European patent EP 1 697 803 B1.
In order'to meet SIL 2, and for the sake of an as high as possible fault detection rate and proportion of so-called Safe Failure Fractions (SFF), diagnostic measures are generally employed in the form of redundant hardware. For example, an additional logic unit for monitoring the main electronic system is located inside the transmitter.
Additional production costs and increased space requirements are incurred due to the additional components required for redundant diagnostics. Also, every additional component requires electrical power, which may be particularly critical with two-wire HART interfaces, where available power is limited.